ANNALES · Ser. hist. nat. · 29 · 2019 · 1
85
received: 2019-01-24                  DOI 10.19233/ASHN.2019.09
OVERVIEW OF TROPHIC LEVELS RECORDED IN TELEOST SPECIES FROM 
NORTHERN TUNISIAN WATERS (CENTRAL MEDITERRANEAN SEA)
Sihem RAFRAFI-NOUIRA
Unité de Recherches Exploitation des Milieux aquatiques, Institut Supérieur de Pęche et d’Aquaculture de Bizerte, Université de
Carthage, BP 15, 7080 Menzel Jemil, Tunisia
Youssouph DIATTA
Laboratoire de Biologie marine, Institut fondamental d’Afrique noire, (IFAN Ch. A. Diop), Université Cheikh Anta Diop de Dakar, BP 
206, Dakar, Senegal.
Christian CAPAPÉ
Laboratoire d’Ichtyologie, case 104, Université de Montpellier, 34 095 Montpellier cedex 5, France
e-mail: capape@univ-montp2.fr
ABSTRACT
This paper reports about the observations made with regard to 21 teleost species comprising 1657 specimens 
from the northern Tunisian coast. These specimens were found in an area with sufficient prey species to allow them 
to live and develop, as confirmed by the size to total body weight relationship. The high values of vacuity index 
are probably due to both sampling and fishing methods. Crustaceans and teleosts are the prey most frequently 
consumed by these species. Additionally, the high trophic levels (TROPH) (± 3.00) indicated that these teleost 
species belong among carnivores. Of all the species examined, only one, Sarpa salpa with TROPH = 2.00, was found 
to be herbivorous.
Key words: Teleost species, trophic level, vacuity index, relation the total length vs the total body weight, 
competition for food, Tunisian coast
REVISIONE DEI LIVELLI TROFICI DI SPECIE DI TELEOSTEI IN ACQUE TUNISINE 
SETTENTRIONALI (MEDITERRANEO CENTRAE)
SINTESI
L’articolo riporta le osservazioni fatte su 21 specie di teleostei comprendenti 1657 esemplari provenienti dalla 
costa settentrionale tunisina. Gli esemplari sono stati trovati in un’area con una quantità di prede sufficiente per 
consentire loro di vivere e svilupparsi, come confermato dal rapporto tra le dimensioni corporee e il peso corporeo 
totale. Gli alti valori dell’indice di vacuità sono probabilmente dovuti sia al campionamento che ai metodi di pesca. 
Crostacei e teleostei sono le prede più frequentemente consumate da queste specie. Gli alti livelli trofici (TROPH) 
(± 3,00) hanno inoltre evidenziato che tali specie di teleostei sono carnivore. Di tutte le specie esaminate solo una, 
Sarpa salpa, con TROPH = 2,00, è risultata erbivora.
Parole chiave: teleostei, livello trofico, indice di vacuità, relazione tra lunghezza totale e peso corporeo totale, 
competizione alimentare, costa tunisina
ANNALES · Ser. hist. nat. · 29 · 2019 · 1
86
Sihem RAFRAFI-NOUIRA et al.: OVERVIEW OF TROPHIC LEVELS RECORDED IN TELEOST SPECIES FROM NORTHERN TUNISIAN WATERS ..., 85–90
INTRODUCTION
Fishery and aquaculture are believed to play an 
important role in Tunisian economy, which explains why 
studies related to these patterns have been the subject of 
several papers (see Bradaï, 2000; Rafrafi-Nouira, 2016). 
The entire Tunisian coast, including lagoons, has been 
continuously investigated since Vinciguerra (1882) to 
assess, in qualitative and quantitative terms, the status 
and the biodiversity of local ichthyofauna. Several 
studies focused on fish species occurring in northern 
areas (Castany, 1955; Ben Mustapha, 1966; Lubet & 
Azzouz, 1969; El Kamel-Moutalibi, 2014; Mnasri-
Sioudi, 2014; Rafrafi-Nouira, 2016).
The aim of this paper is to point out the 
interrelationships between fish species caught off Ras 
Jebel and its closely related areas, and their potential 
preys. Thus, the trophic levels were determined for 
some species of commercial interest commonly 
observed in fish markets. Following Stergiou & Karpouzi 
(2002), estimation of trophic level plays a major role 
in monitoring fishery resources and their effect on 
ecosystems. Additionally, following Froese et al. (2011), 
the size versus total body weight relationship was 
calculated for each species to point out if they found 
sufficient food in the wild to live and develop.
MATERIAL AND METHODS
Of the 124 fish species captured in northern Tunisian 
waters, 21 teleost species were targeted, comprising 
1657 specimens sampled for this study between 2010 
and 2015. According to the information provided by 
experienced local fishermen, the specimens were 
collected throughout the year off the northern and 
northeastern Tunisian coast, including the Gulf of Tunis 
(Fig. 1), by commercial fishing vessels using trawl over 
sandy and muddy bottoms, and gill nets and longlines on 
rocky bottoms, at depths ranging from 50 to 200 m. Each 
sampled specimen was identified using books and field 
guides, such as Whitehead et al. (1984-1986), Louisy 
(2002) and Quéro et al. (2003). All fresh specimens were 
delivered to the laboratory, where they were measured 
for total length (TL) to the nearest millimetre and weighed 
for total body weight (TBW) to the nearest gram.
For each specific sample the Shapiro–Wilk’s test of 
normality was performed, with P < 0.05. The Chi-square 
test was used to determine significance (P < 0.05). The 
total length (TL) to total body weight (TBW) relation 
was used to complement the feeding studies following 
Froese et al. (2011). This relationship is TBW = aTLb, and 
was converted into its linear regression, expressed in 
decimal logarithmic coordinates, and correlations were 
assessed by least-squares regression. Like so: log TBW = 
log a + b log TL. Significance of constant b differences 
was assessed to the hypotheses of isometric growth if b 
= 3, positive allometry if b > 3, and negative isometry if 
b > 3 (Pauly, 1983). Comparison of means was carried 
out using ANOVA. These two latter tests were performed 
using the STAT VIEW 5.0 logistic model.
Once the fresh specimens were collected, their 
stomach contents were immediately removed by 
dissection, sorted and identified to the lowest taxonomic 
level (species level where possible), using taxonomic 
keys and field guides (Perrier 1964, 1975, Louisy, 2002). 
The prey items were counted and weighed to the nearest 
decigram after removal of surface water by blotting 
them with tissue paper. When prey items found in the 
stomachs were incomplete, the prey count was based on 
the number of different typical parts, such as beaks for 
cephalopods, claws and legs for crustaceans, carapaces 
for decapod crabs, shell and foot for bivalves, operculum 
and shell for gastropods, and the whole vertebral 
column and otoliths for teleost species. We assumed 
two or more prey species if the legs of crustaceans were 
different in size and shape, and a single prey species if 
they were very similar. The same methodology was used 
for determining vegetal preys. Preys not identified in the 
laboratory were preserved in 10% buffered formalin to 
be subsequently examined by specialists.
Fig. 1: Map of Tunisia indicating the capture area 
(rectangle) of 21 teleost species from the northern 
Tunisian coast. GT: Gulf of Tunis; GH: Gulf of 
Hammamet; GG: Gulf of Gabès.
Sl. 1: Zemljevid Tunizije z označeno lokaliteto 
(pravokotnik) ulova 21 vrst kostnic ob severni tunizijski 
obali. GT: Tuniški zaliv; GH: Hamameški zaliv; GG: 
Gabeški zaliv.
ANNALES · Ser. hist. nat. · 29 · 2019 · 1
87
Sihem RAFRAFI-NOUIRA et al.: OVERVIEW OF TROPHIC LEVELS RECORDED IN TELEOST SPECIES FROM NORTHERN TUNISIAN WATERS ..., 85–90
The analyses of food composition and feeding 
habits of these 21 species were based on the following 
indices suggested by Hureau (1970), Hyslop (1980) 
and Rosecchi & Nouaze (1987). The food composition 
and feeding habits of C. conger were studied using the 
following indices suggested by Hyslop (1980): 
• Vacuity Index, VI = number of empty stomachs/
total number of stomachs x 100;
• Mean number of prey per stomachs: MN = total 
number of prey ingested/total number of full 
stomachs;
• Percentage of numerical abundance: %N = 
(number of prey item i/total number of prey) x 
100; 
• Percentage in weight: %W = (weight of prey item 
i/total weight of all prey) x 100;
• Percentage of frequency of occurrence: %F = 
(number of stomachs containing prey item i/total 
number of full stomachs) x 100.
The trophic level (TROPH) of each species area 
was calculated using TrophLab (Pauly et al., 2000), a 
standalone Microsoft Access routine for estimating 
trophic levels, downloadable from FishBase (Froese & 
Pauly, 2014). Statistical differences (P < 0.05) in basic 
diet composition as a function of size and season were 
established by applying the Chi-square test (Sokhal & 
Rohlf, 1987).
The trophic level for any consumer species i is 
where Trophj is the fractional trophic level of prey 
j, DCij is the fraction of j in the diet of i, and G is the 
total number of prey species (Pauly et al., 1998; Pauly & 
Christensen, 2000; Pauly & Palomares, 2000): 
All categories of preys identified in the present 
study were used to evaluate the trophic level of each 
teleostean species.
Following Stergiou & Karpouzi (2002), the trophic 
level values ranging from 2.0 to 4.5 and 3 categories of 
species were taken into consideration: pure herbivores 
= 2.0–2.1, omnivores with a preference for vegetable 
material = 2.1–2.9, omnivores with a preference for 
animal preys 2.9–3.7, carnivores feeding exclusively on 
animal preys =3.7–4.5.
RESULTS
All data recorded and calculated in the present paper 
are summarized in Table 1. The TL-TBW relationships 
revealed positive allometry in 13 species, low negative 
allometry in 3 species, and negative allometry in 5 
species. The lowest negative allometry was recorded in 
Dicentrarchus labrax with b=1.23.
The vacuity index (VI) reached high values in 16 
species, low values in 5 species, and in a single species, 
Sarpa salpa, it equalled 0.00. In this species, all the 
stomachs observed contained food or remains of food 
already described in materials and methods.
Overall, the two important zoological groups found 
in the guts were crustaceans and teleosts. Both groups 
were found together in 11 species, while teleosts were 
present in 20 species altogether. A single species, S. 
salpa, did not consume such preys, rather foraging for 
algae and seagrass. Among other groups also found 
in the stomach contents, cephalopods, annelids and 
sipunculids were the most frequent.
The trophic level (TROPH) reached high values - i.e., 
close to or higher than 3.00 - in 16 species. Conversely, it 
displayed low values in 5 species: Dentex dentex (2.37), 
Diplodus annularis (2.57), D. puntazzo (2.24), D. vulgaris 
(2.73), which belong among omnivorous species, and in 
S. salpa (2.00), which is a pure herbivorous species. The 
TROPH of species caught in Tunisian waters is generally 
close to the data recorded by Stergiou and Karpouzi 
(2002), except in those concerning sparid species, 
which ranged between 3.80 and 4.50.
DISCUSSION
The size (TL) versus total body weight relationships 
exhibited positive allometry for most of the species 
studied in the present paper, indicating that they found 
in the wild sufficient prey to be able to live and develop 
in this area. The northern coast of Tunisia revealed high 
biodiversity, including potential prey species belonging 
to several zoological groups (Rafrafi-Nouira, 2016). All 
species presented herein are targeted by fishermen for 
local consumption or export, which enhances their 
commercial interest and increases their value for the 
local economy. Conversely, only 7 species displayed 
negative allometry, which phenomenon could be 
explained by sampling hazards, but competitive 
pressure for food, which reduces the availability of 
prey familiar to certain species, cannot be totally ruled 
out either.
Conversely, the vacuity index (VI) displayed high 
values in most species, which could be explained by 
the non-availability of prey in the wild despite the local 
biodiversity richness. Such a pattern could also be the 
result of sampling periods, and the availability of certain 
prey could vary according to the season (Rafrafi-Nouira, 
2016). Sampling methods and use of fishing gears 
cannot be totally excluded either (Sallami et al., 2014; 
Rafrafi-Nouira et al., 2016). All specimens sampled off 
the northern Tunisian coast were caught by trawling and 
generally spent considerable time in nets prior to being 
landed, therefore certain prey was completely digested 
and the stomachs of predators were thus found empty 
when analysed. This hypothesis is corroborated by the 
digested remains of prey found in the stomach contents 
ANNALES · Ser. hist. nat. · 29 · 2019 · 1
88
Sihem RAFRAFI-NOUIRA et al.: OVERVIEW OF TROPHIC LEVELS RECORDED IN TELEOST SPECIES FROM NORTHERN TUNISIAN WATERS ..., 85–90
which remained unidentifiable. Similar patterns were 
observed in previous studies about food and feeding 
habits of species from northern Tunisian waters (Mnasri 
et al., 2012; El Kamel-Moutalibi et al., 2013; Sallami et 
al., 2014; Rafrafi-Nouira et al., 2016).
Two zoological groups prevailed in the stomach 
contents: crustaceans and osteichthyans, thus confirming 
previous observations concerning other species 
inhabiting the same marine areas (Rafrafi-Nouira, 2016). 
Similarly, other preys were found, such as cephalopods, 
Tab. 1: Parameters recorded in 21 teleost species collected from the northern coast of Tunisia. * Data from Sellami 
et al. (2015); ** Data from Rafrafi-Nouira et al. (2015); VI: vacuity index; C: crustaceans; T: teleosts; OG: other 
groups. TROPH 2: data from Stergiou & Karpouzi (2002). 
Tab. 1: Izračunani parametri za 21 vrst kostnic, ujetih ob severni tunizijski obali. * Podatki iz vira Sellami et al. 
(2015); ** Podatki iz vira Rafrafi-Nouira et al. (2015); VI: indeks polnosti; C: raki; T: kostnice; OG: druge skupine. 
TROPH 2: podatki iz Stergiou & Karpouzi (2002). 
Species Total length (TL) vs total body weight (TBW) %VI C T OG TROPH 1 TROPH 2
Gnathophis mystax  
(Delaroche, 1809) *
log TBW = – 5.88 + 3.09log TL,  n = 48, r = 0.96 60.41 + + + 3.51 3.55
Belone belone 
(Linnaeus, 1758)
log TBW = – 5.79 + 2.94log TL, n =13, r = 0.97 69.23 - + - 4.50 -
Epinephelus 
marginatus (Lowe, 
1834)
log TBW = – 5.14 + 3.11 log TL, n = 20, r = 0.99 65.00 + + + 3.51 4.13
Serranus scriba 
(Linnaeus, 1758)
log TBW = – 5.17 + 3.13 log TL, n = 76, r = 0.98 21.05 + + + 3.27 3.70
Dicentrarchus labrax 
(Linnaeus, 1758)
log TBW = – 0.58 + 1.23 log TL, n = 16, r = 0.91 75.00 + + - 4.20 -
Sciena umbra 
(Linnaeus, 1758)
log TBW = – 5.32 + 3.15 log TL, n = 63, r = 0.98 69.84 + + + 3.41 3.80
Dentex dentex 
(Linnaeus, 1758)
log TBW = – 4.34 + 2.75 log TL, n = 16, r = 0.97 81.25 + + + 2.37 4.50
Diplodus annularis 
(Linnaeus, 1758)
log TBW = – 3.88 + 2.58 log TL, n = 120, r = 0.96 70.45 + + - 2.57 3.40
Diplodus puntazzo 
(Cetti, 1777)
log TBW = – 4.77 + 2.98log TL, n = 31, r = 0.99 56.10 - + + 2.24 3.30
Diplodus sargus 
(Linnaeus, 1758)
log TBW = – 4.89 + 3.04log TL, n = 58, r = 0.98 23.07 + + + 3.09 3.38
Diplodus vulgaris 
(Linnaeus, 1758)
log TBW = – 4.89 + 3.02 log TL, n = 112, r = 0.96 94.00 - + + 2.73 3.70
Lithognathus 
mormyrus (Linnaeus, 
1758)
log TBW = – 5.16 + 3.10 log TL, n = 43, r = 0.96 93.02 - + - 3.50 3.50
Oblada melanura 
(Linnaeus, 1758)
log TBW = – 5.18 + 3.11 log TL, n =32, r = 0.98 68.75 - + - 2.80 3.10
Sarpa salpa 
(Linnaeus, 1758)
log TBW =– 4.93 + 3.03 log TL, n =109, r = 0.93 0.00 - - + 2.00 2.50
Sparus aurata 
Linnaeus, 1758
log TBW = – 4.69 + 2.91 log TL, n = 80, r = 0.98 37.5 + + + 3.81 3.42
Labrus merula 
Linnaeus, 1758
log TBW = – 5.49 + 3.27 log TL, n =51, r = 0.99 80.40 + + - 3.20 3.47
Labrus viridis 
Linnaeus, 1758
log TBW = – 3.79 + 2.53 log TL, n = 65, r = 0.97 65.00 - + + 3.38 3.84
Symphodus melops 
(Linnaeus, 1758)
log TBW = –5.05 + 3.12 log TL, n = 68, r = 0.97 76.19 - + + 3.26 -
Symphodus tinca 
(Linnaeus, 1758)
log TBW = – 5.16 + 3.10 log TL, n =42, r = 0.97 68.96 - + + 3.32 3.26
Chelon labrosus 
(Risso, 1827)
log TBW = – 4.09 + 2.61 log TL, n =14, r = 0.89 95-94 - + - 3.50 -
Scorpaena porcus 
Linnaeus, 1758 **
log TBW = – 4.60 + 3.09 log TL, n =715, r = 0.96 41.11 + + + 3.48 3.82
ANNALES · Ser. hist. nat. · 29 · 2019 · 1
89
Sihem RAFRAFI-NOUIRA et al.: OVERVIEW OF TROPHIC LEVELS RECORDED IN TELEOST SPECIES FROM NORTHERN TUNISIAN WATERS ..., 85–90
annelids, bivalves, and echinoderms, the number and 
weight of these animals depending on the species, and 
on the prey and predator sizes. Additionally, ontogenic 
changes were probably related to the biological 
environment and therefore prey availability.
The trophic levels of the 21 sampled species from 
northern Tunisian waters are similar to those estimated 
by Stergiou & Karpouzi (2002). Of these species, 17 
could be considered top predators playing an important 
role in the regulation of the local marine ecosystem. 
Inter- and intraspecific competitive pressure for food 
cannot be completely avoided, which was probably 
the case with the sparid species, which occupied a 
lower TROPH level than other species, as sea grass and 
algae were recorded in their guts. Such findings could 
be considered as occasional or at least the result of a 
local abundance of marine plants that fishes would feed 
on in addition to other prey items. S. salpa is the best 
example of the effect of such abundance, as indicated 
by its low TROPH = 2.00 and VI = 0.00; namely, large 
amounts of algae and seagrass were found in the guts of 
the examined specimens throughout the year.
The study of food and feeding habits presented in 
this paper not only showed that viable populations 
of several animal species occurred in the area, but 
also enhanced the knowledge of local biodiversity. 
However, monitoring of fishery activities following 
recommendations and suggestions included in CIESM 
(2018) should be carried out to avoid drastic declines 
of populations, as was the case in other marine areas 
throughout the Mediterranean Sea.
ACKNOWLEDGEMENTS
The authors are grateful to the fishermen of the study 
area who kindly provided us specimens. They wish to 
thank also two referees for helpful and useful comments 
allowing us to improve the scientific quality of the paper.
PREGLED TROFIČNIH NIVOJEV PRI RIBAH KOSTNICAH VZDOLŽ 
SEVERNOTUNIZIJSKIH VODA (OSREDNJE SREDOZEMSKO MORJE)
Sihem RAFRAFI-NOUIRA
Unité de Recherches Exploitation des Milieux aquatiques, Institut Supérieur de Pęche et d’Aquaculture de Bizerte, Université de
Carthage, BP 15, 7080 Menzel Jemil, Tunisia
Youssouph DIATTA
Laboratoire de Biologie marine, Institut fondamental d’Afrique noire, (IFAN Ch. A. Diop), Université Cheikh Anta Diop de Dakar, BP 
206, Dakar, Senegal.
Christian CAPAPÉ
Laboratoire d’Ichtyologie, case 104, Université de Montpellier, 34 095 Montpellier cedex 5, France
e-mail: capape@univ-montp2.fr
POVZETEK 
V prispevku avtorji poročajo o rezultatih, ki se nanašajo na 1657 primerkov rib kostnic, ujetih vzdolž severnotu-
nizijske obale, ki pripadajo 21 vrstam. Primerki so bili ujeti v okolju, bogatem s plenom, kar je razvidno iz odnosa 
med velikostjo in telesno maso. Visoke vrednosti indeksa polnosti prebavila so verjetno posledica vzorčevalnih in 
ribiških metod. Najbolj pogosti skupini plena so raki in kostnice. Poleg tega visoki trofični nivo (TROPH) (± 3.00) 
potrjuje, da so obravnavane kostnice predvsem plenilke. Med vsemi obravnavanimi vrstami je le salpa rastlinojeda 
(TROPH = 2.00).
Ključne besede: kostnice, trofični nivo, indeks polnosti, odnos med telesno dolžino in maso, kompeticija za 
hrano, obala Tunizije
ANNALES · Ser. hist. nat. · 29 · 2019 · 1
90
Sihem RAFRAFI-NOUIRA et al.: OVERVIEW OF TROPHIC LEVELS RECORDED IN TELEOST SPECIES FROM NORTHERN TUNISIAN WATERS ..., 85–90
REFERENCES
Ben Mustapha, A. (1966): Présentation d’une carte 
de pêche pour les côtes nord de la Tunisie. Bull. Inst. 
Océanogr. Pêche, Salammbô, 1(1), 21-36.
Bradaï, M.N. (2000): Diversité du peuplement 
ichtyque et contribution à la connaissance des sparidés 
du golfe de Gabès. Thesis, University of Sfax (Tunisia), 
600 pp.
Castany, G. (1955): Le Haut-Bassin Siculo-Tunisien. 
Etude de morphologie et de géologie sous-marines. Bull. 
stn. Océanogr. Salammbô, 52, 3-12.
CIESM (2018): Engaging marine scientists and fishers 
to share knowledge and perceptions – Early lessons. 
CIESM Workshop Monograph n° 50 [F. Briand, ed.], 
CIESM Publisher, Paris, Monaco, 218 pp.
El Kamel-Moutalibi, O., N. Mnasri, M. Boumaïza, C. 
Reynaud & C. Capapé (2013): Diet of common torpedo 
Torpedo torpedo (Chondrichthyes:Torpedinidae) from 
the Lagoon of Bizerte (northeastern Tunisia, central 
Mediterranean). Cah. Biol. Mar., 54(2), 209-220.
El Kamel-Moutalibi, O. (2014).  Les élasmobranches 
de la lagune de Bizerte (Nord Tunisien,Centre 
Méditerranée): Biodiversité et biologie de la torpille 
ocellée Torpedo torpedo (Linneaus,1758). Thesis, 
University of Carthage (Tunisia), 233 pp.
Froese, R., A.C. Tsikliras & K.I. Stergiou (2011): 
Editorial note on weight-length relations of fishes. Acta 
Ichthyologica et Piscatoria, 41, 261-263.
Froese, R. & D. Pauly (2014): FishBase. [version 
06/2014] http://www.fishbase.org
Hureau, J. (1970): Biologie comparée de quelques 
poissons antarctiques (Notothenûdae). Bull. Inst. 
Océanogr, Monaco, 68,1-244.
Hyslop, E.J. (1980): Stomach contents analysis: a 
review of methods and their application. J. Fish Biol., 
17, 411- 429.
Louisy, P. (2002): Guide d’identification des poissons 
marins Europe et Méditerranée. Paris, Ulmer édition, 
Paris, 430 pp.
Lubet, P. & A. Azzouz (1969): Etude des fonds 
chalutables du golfe de Tunis. Bull. Inst. océanogr. 
Salammbô, 1(3), 87-111.
Mnasri, N., O. El Kamel, M. Boumaïza, C. Reynaud 
& C. Capapé. (2012): Food and feeding habits of 
the small-spotted catshark, Scyliorhinus canicula 
(Chondrichthyes: Scyliorhinidae) from the northern 
coast of Tunisia (central Mediterranean). Cah. Biol. Mar., 
53(1), 139-150.
Mnasri-Sioudi, N. 2014. Les élasmobranches de la 
côte septentrionale de la Tunisie: Biodiversité et étude 
écobiologique d’une espèce pleurotrême Scyliorhinus 
canicula (Linneaus, 1758). Thesis, University of Carthage 
(Tunisia), 239 pp.
Pauly, D. (1983): Some simple methods for 
assessment of tropical fishes. FAO Fish. Tech. Papers, 
234, 3-10.
Pauly, D., A. Trites, E. Capuli & V. Christensen 
(1998): Diet composition and trophic levels of marine 
mammals. ICES J. Mar. Sci., 55, 467-481.
Pauly, D. & V. Christensen (2000): Trophic levels of 
fishes. In: Fishbase 2000: Concepts, Design and Data 
Sources, (R. Froese., D. Pauly eds), ICLARM, Manila, 
Philippines, pp. 181.
Pauly, D., R. Froese, P. Sa-a, M.L. Palomares, 
V. Christensen & J. Rius (2000): TrophLab Manual. 
ICLARM, Manila, Philippines.
Pauly, D. & M.L. Palomares (2000): Approaches for 
dealing with three sources of bias when studying the 
fishing down marine food web phenomenon. In Fishing 
Down the Mediterranean Food Webs? (F. Briand ed.). 
CIESM Workshop Series, 12, 61-66.
Perrier, R. (1964): La faune de la France illustrée. 
1B. Vers et némathelminthes. Delagrave, Paris, 179 pp.
Perrier, R. (1975): La faune de la France illustrée. II. 
Arachnides et crustacés. Delagrave, Paris, 220 pp.
Quéro, J.C., P. Porché & J.J. Vayne (2003): Guide 
des poissons de l’Atlantique européen. Les Guides du 
naturaliste. Delachaux & Niestlé: Lonay (Switzerland)-
Paris, 465 pp.
Rafrafi-Nouira, S., O. El Kamel-Moutalibi, M. 
Boumaïza, C. Reynaud & C. Capapé (2016): Food and 
feeding habits of black scorpionfish, Scorpaena porcus 
(Osteichthyes: Scorpaenidae) from the northern coast of 
Tunisia (central Mediterranena). J. Ichthyol, 56(1), 107-
123.
Rafrafi-Nouira, S. (2016): Catalogue raisonné des 
espèces de poissons capturées devant Ras Jebel et autres 
régions marines de Tunisie septentrionale: aspects 
morphologiques, biométriques et bio-écologiques. 
Thesis, University of Carthage (Tunisia), 509 pp.
Rosecchi, E. & Nouaze Y. (1987): Comparaison de 
cinq indices alimentaires utilisés dans l’analyse des con-
tenus stomacaux. Rev. Inst. Pêch. Marit., 49, 111-123.
Sallami, B., M. Ben Salem, C. Reynaud & C. Capapé 
(2014): Diet of Mediterranean Moray Eel Muraena helena 
(Actinopterygii: Anguilliformes: Muraenidae) from the 
northeastern Tunisian coast (central Mediterranean). 
Acta Ichthyol. Piscat., 44(4), 273-283.
Sokhal, R.R. & F.J. Rohlf (1987): Biometry. Freeman: 
San Francisco, CA, 859 pp.
Stergiou K.I. & V.S. Karpouzi (2002): Feeding habits 
and trophic levels of Mediterranean fish. Rev. Fish Biol. 
Fish. 11, 217-254.
Whitehead, P.J.P., M.L. Bauchot, J.-C. Hureau, 
J. Nielsen & E. Tortonese (1984-1986): Fishes of the 
North-eastern Atlantic and the Mediterranean, Unesco, 
Paris, Vol. 1., Vol. 2., Vol. 3, 1473 pp.